1. Field of the Invention
The present invention relates generally to a robotic system. More particularly the present invention relates to a method and apparatus for exchanging an object or piece between a robot in the robotic system and the exterior of the robotic system.
2. Description of Related Art
Many robotic systems facilitate the assembly and manipulation of a variety of components or objects. It is necessary that such robots have a way of exchanging these objects with the outside world and have a ready supply of components with which to operate when required to. It is also necessary, from a safety point of view, that personnel are not present in the vicinity of a robot while it is operating. Many industrial robots are extremely heavy and are programmed to perform their operations regardless of any stray or careless personnel entering their environment. A problem exists therefore in how to transfer components to and from a robot without endangering personnel.
One approach has been to contain the robot behind a locked screen, and having a common key for unlocking the screen and operated. The robot can only be operated if the screen is locked and the key is inserted. This means that the robot has to be deactivated before the screen can be unlocked and components can be supplied to or retrieved from the robot usually by personnel entering the robot's operating area.
A disadvantage of this system is that the robot must be stopped each time it is to be supplied with components or components are to be retrieved. This is contrary to the purpose of many robots which is to provide continuous manufacture or other such service.
Another approach has been to supply a robot with components by means of a conveyor belt or other equivalent transport mechanism which becomes inaccessible to personnel when it enters the robot's operating area. This approach is particularly suitable for a robot carrying out a repetitive task and requiring a constant supply of components. Manipulated components are retrieved from the robot by means of an output conveyor belt. Such systems are not suited to many situations in view of their size, complexity and the nature of the task being performed.
However, not all robot systems require a constant stream of supplies, some systems operate in a manner in which they are only supplied or relieved of a component or a batch of components at irregular time intervals. One such system is an automated storage library in which data storage media are transported between storage shelves and read/write devices by a robot. An automated storage library is usually a memory subsystem of a larger data processing system. When data is required by the data processing system the robot is instructed to retrieve a data storage medium, which may be a tape cartridge, and load it into a read/write device so that the data may be accessed by the data processing system.
In an automated storage library there exists a problem of how to introduce or retrieve data storage media from the library without having to stop the operation of the robot, since this would impede the operation of the associated data processing system. It is necessary that any personnel transporting data storage media to the library cannot come into contact with the moving robot.
U.S. Pat. No. 4,864,511 describes an automated storage library enclosed within a circular shelving arrangement. A section of the shelves hinges outward to expose storage racks to the exterior. As the shelf swings outward an articulated wall portion blocks the arc vacated by the hinged shelf. This allows data storage media to be placed in or retrieved from the library while allowing the robot to continue its operations, partitioned from personnel.
A disadvantage of this configuration is that it is mechanically complex. Also, the swinging shelf makes it prone to errors such as the door movement dislodging the data storage media and distortion of the hinge mechanism causing misalignment. Compensatory measures such as shock absorbers for preventing the door from being slammed shut and thus dislodging media from the shelves and means for supporting the shelves to try and prevent distortion of the hinge and misalignment of the shelves can reduce but not eliminate such problems.